A typical combine harvester includes a fore crop cutting mechanism referred to as a header, and a threshing mechanism to which the cut crop is elevated from the header. In many parts of the United States, particularly the Northwestern area, harvesting of grain occurs in hilly and mountainous areas. Such has led to the development of what are commonly referred to as hillside combines.
When harvesting crops from hillsides, it is desirable that the header follow the contour of the field surface. Yet, the threshing and cleaning mechanisms operate better if they preserve a horizontal orientation. That is, it is desirable that the main combine body be prevented from substantial tipping on a longitudinal axis, although a reasonable amount of tipping about a transverse axis is not a serious disadvantage. It is also desirable that the operator cab also be aligned with the threshing mechanism for operator comfort and safety. Hillside combines provide such features.
Hillside leveling combines are typically constructed to be self-leveling about their longitudinal axis. One example system includes a mercury level switch on the main frame which is activated when the starts to transversely tilting as the combine travels on the side of a hill. As such tilting occurs, the mercury switch activates a leveling mechanism to cause the downhill transverse side sets of wheels to move downwardly, and the opposing uphill transverse sets of wheels to move upwardly a corresponding amount. Thus, the cab and threshing mechanisms are maintained level within the degree of leveling capability of the overall apparatus. The combine header is mounted to be pivotal relative to the main frame. The header and wheels are typically interconnected in such a manner that the angle of the header relative to the main frame is compelled to follow that of the wheels. The typical mechanisms by which this occurs includes cables and pulleys interconnecting the wheel angling system relative to the header.
In such combines, of course, the header is positioned forward of the forwardmost pair of transverse wheels. Accordingly, the header reaches a changing slope condition in advance of the wheels reaching that condition. Until such time as the wheel pass the changing slope, the header does not follow the changing contour of the hillside.